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Very lackluster flower production in my collection this year excluding Aconitifolium and Garnet. Last year was much better here. A few of my larger trees in containers that were loaded last year (ie Katsura) have not a single flower this spring. My in ground trees have some flowers, but they are more mature trees.

In my garden it is definitely a bumper year for flowers, in fact it would be easier for me to list the species or cultivars without flowers this year that the other way around. This is my 'Kagiri nishiki'

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Mirabile dictu!!! Today I found flowers and seeds on a witches broom which I have been looking for in vain for years.
I have a circinnatum 'WB Hoyt' which is a witches broom with its spatulate center loce, close internoding etc and today
while studying the plant, lo and behold there they were - flowers and samaras. I feel like an expectant father at 62!.
I pray the flowers and seeds don't drop but I must say as some of my closest friends on the forum know, I have a large
collection of witches brooms and many of them are good size trees and I have never seen a single flower and only 2 people
I know have ever seen seeds on a maple witches broom and 1 of those 2 is the likely world's expert in palmatum witches brooms.
I had to share the news and hope that some others have seen some this year.

A few more notes on flowering. I too have exceptional flowering this year. Not unprecedented, but lots more than most years. It's been hot here--probably 10 days at least that reached over 75 degrees.

But this worldwide proliferation of flowers--it must be a coincidence, right? These plants aren't like bamboo that flower simultaneously wherever they are grown in the world. I can't think of any other explanation. Maybe global warming is giving us another few weeks of photosynthesis every year, but then every year would be better, not just at intervals. I remember that 40 years ago, my father wouldn't plant the vegetable garden until the end of May. Now, I can usually assume that we'll be safe from frost after April 20 or so.

Something else I've noticed much more this year than previously--my palmatum flowers are swarming with pollinators. Not honey bees, but other small bees, wasps, and flies. Many years, it's still to cold when the maples flower for there to be many pollinators out. I bet there will be good seed set.

One other observation that might interest people. Most years, I wander around town collecting seed from the dissected cultivars in hopes of getting some interesting seedlings. As it happens, most of the trees I collect from are isolated, hundreds of yards at least from other palmatums. Some years I get lots of germination, and maybe 10% dissected cutleaf seedlings. Last fall I collected from the same trees as usual, and I think I only have two or three seedlings. Here's what I think may happen. When it's cold, the flowers develop slowly, so one sex is fully mature long before the other sex (I think it's usually males first, but I'm not sure.) There's very little overlap, so the pollen is gone by the time the stigmas are receptive. Little or no self-pollination, few seeds.

This year is hot, so the flowers develop quickly. By the time the pollen is released, the stigmas are ready. Lots of overlap, lots of pollination, lots of seed, especially because the heat also brings out the insect pollinators.

Just guessing about all this.

Some year, if I feel ambitious, it would be fascinating to hand-pollinate a tree such as 'Seiryu' with pollen from a number of other different cultivars, and then keep track after they germinate. I bet we'd get some pretty distinctive results with the different male parents. But I doubt I'll ever be that ambitious.

Has anybody ever germinated much pseudosieboldianum? I got about 500 seeds last fall, but germination is pretty meager. I'm wondering if they will take two years, like griseum.

Interesting theory, Daniel! FYI I have 0% on pseudosieboldianum this year. We'll see if it goes next year.

So, flowers are apparently not worldwide, I don't have a lot in Normandie this spring except on a few plants. AJ aconitifolium is usually covered with flowers, there are only a couple on the entire plant.

More flowers on the palmatums this year in Northern Ireland too
Normally Aconitifolium is the only flowers I can find
This year I also have flowers on Bloodgood, Kiri Nishiki, Viridis, Okagami, Suminagashi, Chitoseyama and Inazuma (these are the ones I have found this far)
I also caught a bumblebee trying for nectar on Bloodgood (sorry the pic is not in great focus .. the bee wouldn't co operate)

the evident different with some years ago in my maples cultivations,is many rain and frost for many days with temperature under 0Â°
another but small different are:a good number of maples,of equal species,never pesticide!only white oil in low %solution in branch with insect and not in total tree branches...and little prune ,because spring prune remove flower...

Just an update, I do have some pseudosieboldianum coming up, but as with Daniel the germination is pretty weak. We'll see if there are more next year. Mine are also from Ed, so the same source behaving differently. (If you're reading, thanks again Ed. Also a few Villa taranto and shirasawanum microphyllum coming up late, now).

K4 do you stratify yours or just sew in flats?

I have a fair amount of cissifolium this year, if it ripens. Anyone have luck with that one?

I stratify mine in bags of peat mix. Four months in the fridge and they start to germinate, then I put them in 8" pots 'en masse' and let them get a little bigger. Later I will tease out the more interesting ones and put them in individual pots.

I stratify mine in bags of peat mix. Four months in the fridge and they start to germinate, then I put them in 8" pots 'en masse' and let them get a little bigger. Later I will tease out the more interesting ones and put them in individual pots.

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Thanks. I'll bet it's that fridge time that accounts for the higher hit rate, especially with a somewhat colder climate maple like pseudosieboldianum. We definitely don't get 4 months of cold, but if I tried to put them in the fridge my wife would threaten to divorce (or commit) me... :)

Emery-
That cold stratification in the fridge at 38-39F REALLY increases the % germination as you thought.
There is a quantum difference in germination rates between trays put in the fridge for 90-120 days and
trays overwintered outside - huge difference.